水稻根际沉积碳迁移及其关键功能微生物驱动过程研究

Rhizodeposition is a very important source of soil organic carbon and energy for microbial activity in soil, however, the fast turnover rate, complexity and variability of the rhizodeposition carbon, resulted its fate is still unclear. The transfer of rhizodeposition carbon and its key functional microbial mechanisms can also be the basis for revealing the paddy soil carbon cycles. However, due to the experimental skills and tools shortcomings, rhizodeposition carbon transfer and its key functional microbial mechanisms, its relationships and the coordination mechanism of environmental factors is still lack. Therefore, in this project, the 13C isotope labeling technology and in-situ soil column experiment combined with rhizo-box were taken to quantify the horizontal and vertical transfer of rice rhizodepostion carbon and its dynamic distribution and turnover rate in different carbon pools. The microbial biomarkers (13C-PLFA and DNA/RNA) technology will be also used to analyze the dynamic changes of the activity, community and composition of the microbial functional groups which participated in the transfer process of rhizodepostion carbon. Based on the theories of metrology and statistics, the influences of soil environmental factors and management practices on the transfer of rhizodepostion carbon and its key microbial process will also be discussed. The project will provide a scientific basis for understanding the carbon cycle process in paddy ecosystems and strengthen soil sustainable management.

根际沉积碳是土壤有机质的重要来源，其代谢周转快，具有复杂性和多变性，这部分碳的命运还不十分清楚。根际沉积碳迁移过程与关键功能微生物作用机理研究是揭示稻田碳循环机理的基础之一。但受实验技术和手段的限制，目前关于根际沉积碳迁移过程与关键功能微生物的关系，及两者与环境因子的耦合机理缺乏系统研究。因此，本项目以“根际沉积碳–关键微生物”为主线，采用碳同位素示踪技术结合原位土柱和多隔层多室根箱法量化水稻全生育期根际沉积碳水平和垂直方向的迁移及其分配动态与周转速率；综合应用微生物标识物技术与基于13C–DNA/RNA为基础的环境基因组学等分子生物学方法，深入探讨参与根际沉积碳迁移的关键功能微生物活性、区系和结构等动态变化特征；结合计量学和统计学原理，探讨根际沉积碳迁移及其关键功能微生物驱动过程与土壤环境要素和管理措施的内在联系，为深入了解稻田碳循环过程与加强稻田土壤可持续管理提供理论依据。

根际沉积碳是土壤有机质的重要来源，其代谢周转快，具有复杂性和多变性，这部分碳的命运还不十分清楚。根际沉积碳输入过程与关键功能微生物作用机理研究是揭示稻田碳循环机理的基础之一。通过本项目的研究，发现1）施氮与干湿交替有利于水稻的生长发育，既节水同时也能促进光合碳（通过根际沉积作用）向土壤的输入及其稳定性，从而提高土壤的固碳能力；2）施氮使水稻光合碳在不同时期的输入提高34-381%。其中进入土壤中的光合碳提高0.9-1.9倍； 3）不同可利用碳氮的施用显著影响土壤微生物群落组成。微生物易利用的可溶性羧甲基纤维素钠（CMC）和氮肥的联合施用降低了来源于根际沉积碳的革兰氏阳性(G+)/革兰氏阴性(G-)比值，导致了革兰氏阳性(G+)和真菌丰度的降低，而单施氮肥则是刺激了G-和放线菌的增长。4）发现微生物对根际沉积碳利用的变化和土壤微生物群落的演替主要发生在水稻生长的早期阶段氮肥施用可以改变根际沉积物对微生物组成的影响，这主要体现在G+细菌的增加，这可能会促进根际沉积碳从根际向非根际转移。该研究为完善农田土壤碳循环理论框架，为稻田土壤有机碳的调控提供理论支持。. 项目实施期间，发表相关研究的标注论文9篇，包括Soil Biology and Biochemistry、Biology and Fertility of Soils 等SCI一区论文5篇。，项目负责人获德国“洪堡学者”（Humboldt Research Fellowship Programme for Experienced Researchers）资助；培养博士研究生1名，硕士研究生2名。